Like most middle aged men, I had a car crisis. So, after convincing my wife that an Imola Red BMW M Roadster isn’t “chick magnet red,” I bought my dream car. Of course, the dream is never the reality. I rarely drove the M. Summers were too wet and hot (real men don’t drive a convertible with the top up and the a/c on). Fall was too wet. Ah, winter in Florida! It’s the best ‘vert weather but… I just got a new daily driver. So Emily became a garage queen. And died.

Yesterday, I went out to drive her for the first time in two weeks. Unlike The Grand National, she’s never failed to start. But this time, key in, quick turn and nada. The dash lights were on but she didn’t even bother emitting the dreaded click click click sound. A dead battery was the blindingly obvious call. So I rolled her out of the garage, grabbed the jumper cables, opened the trunk, removed the battery cover and– remembered that jump starting a car is generally a bad idea.

Jump starting a modern car is two kinds of dumb. First, we’re talking dumb and dumberer, or, if you prefer, the Darwin factor. That’s when you accidentally reverse the cables and/or cause so much sparking that the battery blows. Second, there’s the small matter of an overly sensitive $1k electronic control unit that can up and die from a spike in the voltage transmitted from the running car to the dead car via Old Sparky– I mean jumper cables.

Some jumper cables now include a special resistor to reduce voltage spike. Some manufacturers also include a jumping block off the battery, which should help prevent battery explosions. But, as you’ve read here, no one reads the owner’s manual anymore. And I’m a lawyer; I don’t trust anyone, with anything, ever.

As an alternative, Sears sells several battery chargers. I reckon they’re a must for any vehicle driven less than once a week. So I tested the Sears DieHard 10/2/50 amp Automatic Battery Charger. The unit MSRPs at $64.99, but way-hey! As of December 23, 2007, it was on sale for a bargain price of only $39.99.

The Diehard charger is your basic, garden variety metal box with one analog battery charging gauge, two leads (for power on and full charge) and a three-way switch. It has two plugs, a 110 amp wall plug (not grounded) and two small jumper cable style wires with a red and black clamp. The Diehard does so with a vengeance; the heavy and sturdy block weighs in at eleven pounds.

So, connect the Diehard to your Diehard battery (or similar), red to red, black to black (or brown, as apparently some car companies didn’t get that memo regarding the international colors for positive and negative). Select the style of charge, plug in the device and wait. The Diehard offers spark proof protection in automatic mode, and even includes a Darwin feature for fashion victims who insist on hooking up red to black and black to red because it’s more aesthetically pleasing.

The Diehard Charger offers three settings depending on your needs. The 50 amp setting is similar to a jump from another car and should allow most cars to start up right away (though I would still give it a minute or two, and keep in mind the warning above, though the voltage from the Diehard is delivered spike free according to Sears).

If you’re not planning on driving the vehicle straight away, set the Diehard in the ten amp mode and wait about two hours. A blinking light will advise you when the battery is fully charged. WARNING: the Diehard doesn’t have an automatic shutoff; leaving the charger in ten amp mode for extended periods can damage your car’s battery. How lame is that?

I used ten amp mode for my M. A couple of hours later the car started like a dream, and ran the rest of the day without battery troubles.

There’s also a two amp trickle charger mode. This is the mode I SHOULD have been using for my M before I let her die. A trickle charge feeds just enough juice to keep the battery charged and the electrical system refreshed without overcharging the battery. Since most cars continue to draw power when off, a trickle charger also prevents damage to electrical components that seem to freak at low voltage.

I recently sampled a rarely driven loaner 2006 M5. When I picked her up after a short lay-up, the dash was lit up like a Christmas tree with dreaded engine damage warnings. A flat bed to the dealer later, I learned that the low voltage had falsely triggered the warnings. If only I’d learned to live free and Diehard.

Actually, 2A is a little excessive for a trickle charge unless you have an inordinate amount of OFF-state current draw. I wouldn’t leave it on 2A indefinately (or more than a couple of days) or you will eventually dry up the battery. 0.5-1A is the most you should trickle charge at under normal conditions.

Definately don’t trickle charge at 2A if the battery is out of the car.

Agreed! 2A is too much for a trickle. I have read many posts from people smarter than I who recommend that you just allow the battery to run down a bit over the week, then charge it with a 2A over the weekend. This “cycling” will go a lot further on longevitity than will leaving it boiling on a trickle charge.

There are AUTOMATIC trickle chargers that can be left on forever but they cost too much for us!

vtech :
There are AUTOMATIC trickle chargers that can be left on forever but they cost too much for us!

I have the Harbor Freight equivalent of this charger and it shuts off automatically (isn’t that what automatic means?) on the 2A setting. It alternates between the two summer only cars during the winter.

Another trick to keep your battery charged is to disconnect the ground while in storage. Or stop buying BMWs :p

On the old Classic… an E-type Jag that gets coddled in the barn all winter having various projects lovingly taken care of, the ground gets disconnected every time it is parked for more than a few hours.

For the old beater pickup that is used a few times a year for dump/hay/lumber hauling I hook up the NAPA 2/10 amp charger every few months until it shuts off automatically.

I’ve had one of those for over a year now. My roommate had a bad habit of leaving his XM on in his XTerra & used it quite frequently in the 50amp mode. It worked great. I’ve also used it a couple times for similar purposes.

It seems lame to not have an automatic shutoff in 10 amp mode. 2 amps will dry up a battery in a few short weeks if left on continuously. For my money, you can’t go wrong with the Battery Tender. The “junior\'” version is selling for around $20. Of course this is assuming that one actually hooks it up so that there will not be a need for a 50 amp charger.

I’ve got one of those jump starters that’s essentially a car battery in a plastic box with two jumper cable leads coming off of it. These work well for jumping off a car where the battery is not dead, just no longer strong enough to start the car. Mine has a built in 2/4/6 amp charger with automatic shutoff and it works like a champ. One device, two uses, $80. I think I picked this one up at a Pep Boys.

Timoted:
I agree – I use the “Gel Cell” type of Battery Tender on my motorcycle (which has a sealed battery). The “auto-shutoff” feature works great; I can leave it connected for months with no issue. I’m sure that it could keep a full-sized car battery charged, as long as there’s not a lot of standby power required by the vehicle.

After inadvertently using a ’70s vintage battery charger to boil the ten year-old Delco Freedom II on my ’88 Caprice, I bought a Battery Tender Plus that continues to keep my Impala SS garage queen fully satisfied. It’s a shame that Deltran doesn’t make a product to satisfy the other queen in my life…

– As others have mentioned, the 2A setting is too high for a trickle charge…you wouldn’t want to leave it hooked up for a long period of time.

– The 50A setting isn’t really high enough to start a car with a completely dead battery – though it will probably work for a lawn tractor, or if your battery still has a decent charge. Also, unless I’m mistaken it’s a temporary boost…and you’re not supposed to leave it at that setting for very long because the charger could overheat. If you want a charger that can actually start a car with a completely dead battery you need one of the larger 200A roll-around units.

– It’s pretty tough to fry your car’s computer by jump-starting unless you make a fairly major mistake. If you’re that concerned about it, hook up the cables with both vehicle’s ignitions turned off – and then start the ‘good’ vehicle after the cables are connected. I generally hook the leads on the ‘good’ vehicle directly to the battery, and on the ‘bad’ vehicle I hook the positive to the battery and the negative to a good ground – and this one should be hooked up last, so that if there are any sparks they’re away from the battery and don’t have the potential to cause an explosion. Some folks won’t hook the negative cable directly to the battery on either vehicle, but realistically there isn’t a difference so long as the last connection you make is the one that isn’t hooked directly to the battery.

I find it a bit odd that the author complained about the way the charger looked – after all, it isn’t like a charger is something I’m going to leave sitting around on my coffee table. My chargers (I have 4) generally stay out in the garage, and the kind of folks who spend time in my garage aren’t usually the type to complain about my unstylish battery chargers.

I have a Diehard charger similar to this one, and it has proven to be a pretty reliable unit. At one point I even ran mine over with a truck, and after bending the cover back into shape and checking the wiring (to make sure none of the wires were disconnected or damaged) I plugged it back in and it still works fine. However, after being run over by a 6,000 pound truck my charger is even less stylish than the one in the article.

I bought one of these last summer at Sears and when I unpacked the box, the mode switch was snapped off and rattling around inside the old-school style case. I quickly ran back to town and swapped it for another one. When I got back to my shop — yessir that one was broken as well. Back to Sears and having opened the last of the three the had on the shelf; yep — that one was broken too.

Fool me twice… I went to Tractor Supply and picked up a Schumacher multi-mode unit for about the same money. For my coin, I got a modern heavy duty case and “smart” mode-switching built it. I have since bought two additional Schumacher trickle units, as well. These are first class chargers that should be in everyone’s shop.